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We have been using the 68LC302 for decades without major problems. We have designed a new product using the same circuitry around the 68LC302 as before but we can't get it to serial boot. PA5, PA7, PA12

Question asked by Daniel O'Sullivan on Mar 23, 2017
Latest reply on Mar 28, 2017 by TomE

We have been using the 68LC302 for decades without major problems. We have designed a new product using the same circuitry around the 68LC302 as before but we can't get it to serial boot. PA5, PA7, PA12 & DISCPU are all low for serial boot but it won't echo data sent to SCC1. The clock is running correctly but the CPU resets every ~4.2uS, with internal activity seen on /DTACK synchronous to this. It isn't the MAX691A reset chip, the reset pulses are from the CPU. We have built 2 prototypes and both behave the same. We've been checking this from every angle for days. Help!

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